Problem: How many significant figures does $0.05100$ have?
Solution: Identify the non-zero digits and any zeros between them. These are all significant. $0.0{51}00$ Leading zeros are not significant. $\color{orange}{0.0}{51}00$ Since there is a decimal, trailing zeros are significant. $\color{orange}{0.0}{5100}$ Counting all the significant digits gives us 4.